inNewZealandPastoralFarming

Editedby:PeterAnderson,MartinHawke,BrettHobson,RichardLucas,MichaelO’Connor,StephenWhittaker

SaltUse

of

ForwardandAcknowledgements

Introduction 1.0Brief history of salt 1.1Current uses 1.2NZ salt production 1.3 SodiuminPlantsandAnimals 2.0

Sodium in Plants 2.1Function of Na in Ruminants 2.2

SodiuminNZPastoralSystems 3.0

Sodium content of soils 3.1Sodium content of pasture 3.2Sdium defi ciencies in grazing livestock 3.3

TopdressingPastureswithSalt 4.0

SaltSupplementsforLivestock 5.0

Salt Products 5.1Indications for Use 5.2Specifi c Applications 5.3 Dairy Cows 5.3.1 Beef Cattle 5.3.2 Sheep 5.3.3 Other species 5.3.4 Salt and Supplementary Feeds 5.3.5

UseofSalttoInfluenceGrazingBehaviour 6.0

Use of salt to infl uence grazing intensity 6.1Livestock “salt mines” 6.2

AreasofUncertainty 7.0

Sodium and Bloat 7.1Sodium and Bearings 7.2 Salt, feed intake and production 7.3

References 8.0

ContentsEdited by: Richard Lucas, Michael O’Connor, Stephen Whittaker, Peter Anderson, Martin Hawke, Brett Hobson

inNewZealandPastoralFarmingSaltU

seo

f

Common salt is sodium chloride, NaCl. Sodium (Na) is essential for animal health and production but is not required for pasture growth. The need to supplement pastures or supply salt to livestock is dictated by the Na requirements of the animal. For grazing animals the Na content of the pastures and their intake is therefore all important. Salt has other uses outside pastoral farming.

In 2004 Dominion Salt funded salt trials at Mt Grand, Hawea Flat. The trials were looking at the use of salt as a tool to manage grazing. The results of that work appear in this booklet. A well attended field day led to plenty of discussion of the work. From the discussion it became apparent that knowledge about Na and the use of salt was variable - some farmers were using salt in multiple applications and their neighbours didn’t consider Na/salt an issue. Knowledge among academics and advisors was also patchy. Recommended study texts and publications for the agricultural industry are often very scant on references to Na. This text will hopefully serve as a reminder that sodium is essential to animal production systems.

“Thereseemstobeverylittlepublishedscientificmaterialpromotingtheuseofsalt.Farmersneedfacts,please”-LawrenceCheetham,Masterton

Lackofsodiumisaproductionlimitingissue.It is easily fixed with salt.

The value of salt in the diet of animals and humans was recognized hundreds of years before the nature and extent of its need were established. The value of supplementary salt for cattle was first demonstrated experimentally in 1847 but the effect of salt deprivation on

lactating cows was not reported until 1905. A further half-century passed before sodium rather than chlorine was identified as the element in NaCl which was primarily concerned in animal nutrition (1).

Naturally occurring dietary deficiency of chlorine is rare but chlorine deficiency has been demonstrated experimentally in poultry and calves. Chlorine is found within cells and in body fluids including gastric secretions where it occurs as hydrochloric acid (HCl) and in the form of salts. Chloride ions (Cl-) are also vital respiration functions. Most pastures have more than three times as much chloride content than sodium with little difference between species. Pastures therefore invariably provide sufficient chloride for grazing animals.

This booklet summarises the role sodium plays in New Zealand pastoral farming systems and the production benefits salt can provide. Information is drawn predominantly from New Zealand experience. References are numbered, the numbers appearing throughout the text with a full listing at the end of the book. It is hoped that this single publication will provide practical guidance to a wide range of farmers, agricultural consultants, academics and students.

Acknowledgements

Dominion Salt acknowledges the work carried out by our agricultural research scientists, the farmers who have provided their experiences and freely gave their advice, and the job done by the editorial committee in writing and reviewing the data presented.

Foreword

• Salthasbeentradedforthousandsofyears• Salt’scolorfulhistoryiscoveredin“Salt-

AWorldHistory”,MarkKurlansky• Saltisessentialtolife• Itisusedinsignificantquantitiesinarangeofindustriesincludingagriculture

Summary

Introduction 1.0

Use of Salt in New Zealand Pastoral Farming

SaltinPlantsandAnimals 2.0

• Sodium(Na)isvitalforanimalsbutisnotnecessaryforplantmineralnutrition.

• RuminantlivestockrequireNatoregulatethecompositionofallextracellularfluidsincludingbloodandformaintenanceofaconstantpHintherumen.

• Livestockrequirementsvarybutasageneralrulepasturesrequire0.1%Naminimumtosatisfyproduction

• PlantspeciesdifferintheirabilitytotransportNatotheirleaves.PlantswithahigherNa%intheirrootDMthanintheirshootsareNatrophobes,thosewithalowershoot:rootratioof<1.0areNatrophiles

• Lucerneisanexampleofanatrophobicspecies;theNa%inherbagedrymatterfornatrophobesisusuallyunder0.1%Na.

• Ryegrassandwhitecloverareexamplesofnatrophilicspecies;theynormallyhavemorethan0.1%NaintheirherbagebutareoftendeficientforlivestockwhensoilQuickTestvaluesforNaarelessthan5.

Harvested from the sea or wrested from the earth, salt would appear to be one of the humblest commodities. Yet the sodium and chloride it contains are life-sustaining elements.

Common salt is sodium chloride, NaCl. Sea water is the most abundant source on earth and contains 2.5% salt. 2000 years ago the Romans worked out a process for evaporating sea water and produced solar salt. Salt is also found in large underground deposits formed 150 million years ago. Extraction of underground deposits is either by mining or by dissolving in water and artificially evaporating the brine into salt.

Historically salt was highly valued. Roman legionnaires who guarded the Via Solaria, one of the most famous military roads in history, received part of their pay in salt, the “salarium”.

Briefhistoryofsalt 1.1

From this came the modern word “salary”. To this day a good man is “worth his salt” and we take others’ dramatic pronouncements “with a pinch of salt”. In medieval times people partaking of food around the board in the lord’s castle were seated above or below “the salt” according to their station in life.

We have known for thousands of years that animals need salt. Mark Kurlansky (2) writes of humans following animal trails to salt sources, and then using salt to draw animals to them.

Salt has influenced the location of nations and cities, has been the cause of wars, has given rise to superstitions and religious beliefs and is as essential to life as the air we breathe and the water we drink.

Worldwide salt production is estimated at 240M tonnes (2006). China is the world’s largest producer at 48 million tonnes annually. North America produces more than 25% of the global total. Salt’s uses are many and varied, including; for preserving food; preservation of skins and hides prior to tanning; in food preparation and processing; as a raw material in the production

CurrentUses 1.2

of sodium bicarbonate, soda ash, caustic soda, sodium chromate and sodium sulphate; to produce chlorine for bleaches and disinfectants; in water treatment systems; in medicine for the production of saline drips, haemodialysis fluids, eye washes and toothpaste; in agriculture for fertilizer and stock licks; in making up brines for chiller tanks; and for de-icing roads. 15M tonnes are used on USA Highways each year.

New Zealand’s only salt production field is at Lake Grassmere, Marlborough. Solar salt is produced by evaporating seawater using sun and wind during the summer months. In March the salt crust is lifted and stockpiled for processing throughout the year. Yearly production from Lake Grassmere is not sufficient to meet New Zealand’s

salt needs with shortfalls being imported as raw salt for refining in New Zealand, or as refined salt. Major uses are skins and hides processing, food manufacturing, agriculture and water treatment. Supermarket sales account for less that 4% of trading volume. Usage for road and pavement de-icing is minimal but growing.

NZSaltProduction 1.3

Use of Salt in New Zealand Pastoral Farming

Natrophobes 2.1.1

Plants which normally have low sodium content in their herbage dry matter (DM) are known as natrophobes. While their roots may absorb Na from the soil they do not transport much of it to their leaves. Examples of plants which have low herbage Na are lucerne, red clover, Caucasian clover, browntop, timothy and Kikuyu grass. Natrophobic species will all have herbage which is defi cient for ruminants. Values of 0.01% to 0.05% Na will be expected. As ruminant livestock require about 0.1% Na in their diet, pastures which are dominated by natrophobic species will be defi cient.

Table2.1

Pasture and forage species listed as natrophiles or natrophobes with typical Na% values for the herbage dry matter when grown in a fertile soil near the coast with a quick test Na value of 10 (Na suffi cient) and when grown in an inland fertile soil with a Na quick test of 3 (Na defi cient). Numbers in ( ) refer to number of samples from different sites. (Aspinall 2004)

SodiuminPlants:natrophobesandnatrophiles 2.1

Natrophiles 2.1.2

Natrophiles accumulate Na in their herbage. However, in inland areas away from the main infl uences of coastal salt spray, the low soil Na content results in most natrophilic species being unable to take up enough Na to satisfy ruminant requirements. For example, with a QT Na of 2, white clover (0.02% Na) and cocksfoot (0.01% Na) were defi cient at “Mt Grand” near Hawea Flat in west Otago. On the same farm in a sown paddock with QT Na of 3 the herbs chicory and plantain both had suffi cient Na for ruminant nutrition but all other species in the pasture were defi cient (<0.05% Na). (3) Examples of %Na in herbage dry matter of natrophobes and natrophiles when grown in soil with adequate Na and in Na defi cient soil are presented in Table 2.1

Species SoilNa<5(deficient) SoilNa>5(sufficient)

NatrophilesPlantain 0.25 (3) 0.60 (11)Chicory 0.09 (3) 0.70 (10)Turnip leaf 0.08 (3) 0.13 (2)Perennial ryegrass 0.07 (2) 0.14 (6)Cocksfoot 0.06 (5) 0.16 (4)Sub clover 0.02 (2) 0.34 (2)White clover 0.05 (10) 0.16 (15)

NatrophobesBrowntop 0.05 (2) 0.11 (2)Lucerne 0.05 10) 0.06 (33)Caucasian clover 0.02 (2) 0.02 (2)

Other species which are natrophiles are phalaris, Yorkshire fog, prairie grass, Lotus pedunculatus, (e.g. Maku), and tall fescue. Sub tropical natrophobic grasses like Kikuyu grass, paspalum and maize are all low in Na.

Note that the species in Table 2.1 are listed in order of their herbage Na contents. Natrophiles have been defi ned as plants which have higher Na% in their shoots than their roots. Hence their shoot Na/root Na ratio is more than 1. In contrast

natrophobes have shoot Na/root Na ratios of less than 1 because they retain Na in their roots. (4).While this defi nition of high or low Na herbage species is valuable, there is clearly a continuum from extremely natrophilic species with high shoot Na/root Na ratios of more than 3 (phalaris, Yorkshire fog), marginal species such as tall fescue 1.3 and browntop 0.9 and extreme natrophobes such as paspalum, Kikuyu grass and timothy with a ratio of 0.2 (4).

FunctionofSodiuminRuminants 2.2

RoleofSodiuminRuminants 2.2.1

The role of sodium (Na) in ruminants is two fold:(a) In all animals, sodium plays a critical role as

the principle ion (cation) in the extracellular fl uid and in the regulation of the composition of the blood, ensuring that all the cells of the body are maintained in a constant environment.

(b) Rumen Homeostasis: The most important function of sodium in ruminants is the role sodium plays in maintaining a constant pH in the rumen environment. Recycled Sodium in the form of sodium bicarbonates in the saliva is mixed with rumen constituents to maintain an optimal rumen pH of around 5.8-6.3 (5). At this pH range the fi bre digesting microbes exhibit maximum growth and the digestion of plant and forage dry matter (DM) is optimized. The end result of active digestion in the rumen is the soluble volatile fatty acids - acetic, butyric and propionic acids - it is these that require buffering by the sodium bicarbonate in the saliva to maintain that constant rumen pH.

The implication of a depressed digestion of DM at low ruminal pH can be evaluated in term of the effect it has on a reduction of metabolisable energy (ME). When the pH decreases from its optimal 6.3-5.8 range, a loss of approximately 0.7MJME/kg of pasture DM occurs.

Ruminants produce large volumes of saliva - sheep 10-15l/day and cattle 50-150l/day. At any one time the rumen may contain about 50% of the sodium available in the body. This large demand for sodium can not be meet by dietary intake alone. Sodium must therefore be recycled by the animal from the gut before entering the extracellular fl uid. The kidneys are an effi cient mechanism for conserving or excreting sodium as the occasion demands. Thus animals may remain on sub-optimal Na intakes for extended periods before signs of acute Na defi ciency become apparent.

Use of Salt in New Zealand Pastoral Farming Sodium in Plants and Animals

MinimumDailyrequirementsofsodium 2.2.2

The minimum Na requirements for different classes of stock are not known with any degree of accuracy and are based on very restricted experimental data. The principle source of references are from the British Agricultural Council (ARC) and the American National Research Council (NRC) (6). Towers

aValues for sheep reduced by using a lower value for faecal endogenous loss of 5 as opposed to 20 mg NA/kg LW.bAbsorption coeffi cient = 0.91.

& Smith (7), two New Zealand researchers cite similar reference material based on limited New Zealand trial work. It would appear that these dietary requirements are based on the requirement to avoid clinical defi ciency and not optimize production.The following table contains recommendations for grazing animals. Note that salt contains 40% sodium by weight. When converting Na requirements to salt equivalent multiply by 2.5

Table2.2

Estimates of the minimum dietary sodium concentrations required by sheepa and cattle at the given dry-matter intakes (DMI) (after ARC, 1980) from Underwood & Suttle (1)

Liveweight Growthor DMI GrossbNarequirement (kg) production (kg/day) gNa/day %NaDM gNa/kgDM

Lamb 20 0.1 kg /day 0.5 0.35 0.07 0.7 0.2 kg/day 0.8 0.47 0.06 0.6 40 0.1 kg/day 0.83 0.58 0.07 0.7 0.2 kg/day 1.23 0.71 0.06 0.6

Ewe 75 0 0.8 1.0 0.13 1.25Pregnant ewe 75 1 fetus - 1.03 1.0 0.10 1.0 12 weeks term 1.51 1.01 0.07 0.7 75 1 kg/day 1.48 1.2 0.08 0.81Lactating ewe 2 kg/day 2.18 1.8 0.08 0.83 3 kg/day 2.90 2.2 0.08 0.76

200 0.5 kg/day 3.3 2.3 0.07 0.70 1.0 kg/day 4.7 3.1 0.07 0.65Steer 400 0.5 kg/day 5.2 3.9 0.08 0.75 1.0 kg/day 7.3 4.7 0.07 0.65 600 0 5.0 4.5 0.09 0.9 600 12 weeks term 5.8 4.3 0.09 0.9

Cow (Dry) 9.0 7.2 0.8 0.8Cow 600 10 kg/day 9.4 10.3 0.11 1.1(pregnant) 600 20 kg/day 14.0 16.8 0.12 1.2Cow (milking) 30 kg/day 18.8 22.6 0.12 1.2

SodiuminNewZealandPastoralSystems 3.0

• Soilsodium(Na)contentisinfluencedbyNainputinrainfallwhichinturndependsondistancefromthesea,prevailingwinds,mountainsandrainfall.

• IngeneralherbageNaismostlikelytobedeficientininlandareaswhereSoilQuickTest(QT)Navaluesare5orless.

• AcombinationofinlandlocationandpasturedominatedbyanatrophobicspeciessuchasbrowntoporaweedfreelucernestandwillalmostcertainlypresentaNadeficientdiettobothsheepandcattle.

• AreaswhereNadeficiencyinlivestockislikelytobecommonaretheCentralPlateauintheNorthIslandandinlandareasofMarlboroughandCanterburyandCentralOtago.

• WhereNadeficiencyoccursanimalsneedtobesupplementedwithsalt.Therearevariousmethodsavailable(seechapters4and5)

• Signsofdeficiencyincludelossofappetite,abnormallickingandchewing,haggardappearance,lossofproduction

• DiagnosisofNadeficiencyisnotalwaysreliableorpractical

Use of Salt in New Zealand Pastoral Farming

The map of New Zealand (fi gure 3.1) indicates sodium levels for grass growing in unfertilised soils (8). The darkest zone on the map indicates areas in the west and south where grass DM had over 0.15% Na. The medium coloured zones had grass with between 0.05 and 0.15% Na and the light coloured inland zones had less than 0.05% Na. These data refer to sweet vernal which is present in most undeveloped land in the country. The map suggests that the main infl uences on sea spray and therefore on soil Na are strong westerly and southerly winds, mountain barriers, distance from the sea and rainfall. Clearly all inland areas of the South Island are likely to be Na defi cient along with the pumice soil regions of the Central Plateau in the North Island.

SodiumContentofSoils 3.1

Figure3.1PastureSodiumLevelsinUnfertilisedSoils

Southland Waikato

Inputs: kgNa/ha/annum kgNa/ha/annumFertiliser 1 1Rainfall 20 35

Outputs:Milk and meat 4 6Transfer 2 2Leaching 29 40

Balance: -14 -12

Of the four exchangeable cations in soil (Ca, Mg, K and Na), Na is usually present in lowest concentration. Typical soil Na QT values range between 5 and 10. Inland defi cient areas have QT Na values of less than 5 and it is rare for soil Na to exceed 20-25 QT units. However, because Na is the least strongly held cation on soil cation exchange sites, it is frequently the main cation in soil solutions. (9, 10)

Inputs of Na from rainfall in the North Island range from about 120 kg Na/ha/year near the west coast down to about 5 kg Na/ha/year in central districts. It is highly likely that the Central regions of both islands are in negative Na balance and that soils will be depleted of Na over time. This depletion of Na in inland areas is likely to be worse in regions with a low cation exchange capacity (CEC) such as the pumice soils in the Central Plateau. Low CEC, means that soils have a reduced capacity to hold Na ions against leaching.

Sodium budgets on dairy farms have been presented for Southland (11) and Waikato/Taranaki (12). Both regions are considered to have adequate soil and plant Na. Rainfall is the greatest source of Na and leaching is the largest loss. Table 3.1 shows that both regions are in negative Na balance. So even though inputs of Na are high it is likely that losses will lead to declining Na levels in soils and pastures over time. This is particularly the case for intensive dairying where Na output in milk from dairy farms is likely to be greater than from meat production on sheep and beef farms.

The data in Table 3.1 are for typical dairy farms. There will however be considerable variation from year to year in salt inputs and leaching of Na. This variation will be driven mainly by rainfall but grazing management will also have some impact on leaching especially during winter. Variation in leaching losses from Waikato pastures ranged between 13 and 36 kg Na/ha/year depending on rainfall and similar variations in inputs from rainfall may also be expected. (10)

Table3.1

Sodium nutrient budgets for typical dairy farms in Southland and Waikato.

Percentage on oven-dry weight

Over 0.15

Betwenn 0.05 and 0.15

Less than 0.05

Use of Salt in New Zealand Pastoral Farming Sodium in New Zealand Pastoral Systems

SodiumContentofPasturespecies. 3.2

Sodiumdeficienciesingrazinglivestock 3.3

Much of the data on pasture Na comes from mixed samples collected from developed pasture on intensively farmed properties. The botanical composition of those samples is normally about 80% ryegrass and 20% white clover. Both species are natrophiles and can be expected to contain sufficient Na for lactating cows if the soil QT is greater than 5. Where soil test Na levels are low (<5) ryegrass/white clover pasture herbage should be tested for %Na. Actual pasture deficiency levels for various livestock classes are discussed in Chapter 5.

If natrophobic species dominate pastures in inland areas and soil Na is deficient all pastures are likely to be Na deficient and livestock will benefit from salt supplementation. Spreading salt as fertiliser on natrophobic species such as browntop, kikuyu grass or lucerne will not lift Na% in the herbage as much as in natrophilic species such as ryegrass, cocksfoot or white clover. Topdressing salt in such situations is not likely to be effective. Other means of supplementing salt eg. blocks or drenching will be required.

DiagnosisofSodiumdeficiencyinlivestock:Sodium levels in many NZ pastures are low, and falling, as a result of continued leaching and the low proportion of farmers adding salt to their fertiliser requirements. This is possibly due to the fact that sodium is not required by the plant to increase pasture yield and so is not actively promoted by fertiliser companies. Also, sodium deficiencies are difficult to diagnose as specific clinical signs are not directly attributed to sodium and blood tests are not specific to a deficiency.

ClinicalSignsofdeficiency 3.3.1

In ruminants, the initial sign of Na deficiency is the development of a depraved appetite, or pica, which is manifested as an intense craving for salt. Signs include abnormal licking or chewing of wood, soil or the licking of the sweat from other animals. (See section 6.2). These early signs normally become apparent after 2 to 3 weeks of the animals being placed on a sodium deficient diet. In a prolonged deficiency, loss of

appetite is accompanied by the development of a haggard appearance, lusterless eyes and a dry and harsh coat, with reduced milk production and rapid weight loss and/or decreased growth rates. In extreme and prolonged sodium deficiencies, the animals will shiver, become uncoordinated, show general weakness, develop heart arrhythmias eventually collapsing and dieing.

Example1:A classic example of Na deficiency symptoms was recorded in a herd of 45 lactating Holstein-Friesians in 1975. The cows showed increased urination (polyuria), and a 40% decrease in herd milk production. Other signs in the herd included salt hunger, pica and loss of body condition. Cows were seen to be eating the urine soaked straw bedding in preference to hay. These cows were supplemented with 60g salt/cow/day and there was a decrease in urine output and an increase in milk yield over the ensuing 10 days. (13)

Example2:In New Zealand it has been shown that weaner beef Angus cattle grazing pastures that contained 0.08% Sodium (0.8g Na/kg DM)did not grow as well as those on pastures with a sodium content of 3.2gNa/kgDM, whereas weaners on pasture with 1.1gNa/kgDM grew as well as weaners on pasture with 1.7gNa/kgDM. These observations suggest that the requirements for Na, while not meet by herbage containing 0.08gNa/kgDM, is meet if the herbage concentration exceeds 1.1gNa/kgDM. (7)

Example3:Mike O’Connor in 2000 in a salt supplementation trial of milking dairy cows was able to show a 12.8% increase in milk production after the cows were supplemented with 35 g of salt. This response occurred within 2 weeks and continued throughout the trial period. (14)

Grazing ruminants in NZ are unlikely to suffer extreme Na deficiency, but sub optimal production may be common in dairy herds where Na intakes are not optimal as a result of low herbage Na concentration or mixed rations that includes maize silage or Palm kernel (PKM, PKE). Addition of these supplements is now common place on many intensive dairy farms throughout NZ.

DiagnosisofSodiumDeficiency 3.3.2

1) Analysis of Dietary Sodium content: The analysis of sodium in the diet is one method used to estimate the Na status of animals and is frequently used for this purpose. If the dietary Na concentrations are below the minimum suggested (Table 2.2) for the appropriate category of livestock, there is an immediate suggestion of Na deficiency. It is, however, insufficient to

base recommendations solely on dietary Na content given the ability of livestock to select patches of pasture which are high in sodium and the large variation in pasture Na content. Nevertheless, carefully collected forage samples that are representive of the diet of grazing ruminants are extremely valuable and are used extensively in predicting the Na status. Pasture samples should be collected by hand but plastic gloves should be worn, so to avoid contaminating the sample with Na from sweat.

2) Blood samples: Blood sampling for Na status is of little value. Sodium levels in the blood are maintained within a very narrow range. Even in cases where cows were severely deprived of Na and production responses to Na were apparent, no changes in blood sodium occurred.

3) Urine analysis: The Na status of ruminants is maintained largely by regulating the amount of Na that is excreted in the urine. Low urinary Na outputs will therefore reflect low Na intakes. Average Na concentration of less than 3mmol/l are indicative of Na deficiency, while those greater than 7mmol/l indicate an adequate Na intake.

However, accurate diagnosis requires the measurement of 24-hour urine volume and the Na concentration over several days, which under field conditions is not practical. In the field, 10 animals can be urine sampled to increase the likely chance that a deficiency is detected. The results can then be collated in conjunction with pasture analysis and saliva Na content to formulate a better indication of the Na status of the animals.

Use of Salt in New Zealand Pastoral Farming Sodium in New Zealand Pastoral Systems

4) Saliva analysis: The most reliable criterion for diagnosing Na defi ciency is to analyse the relative Na and potassium (K) concentrations in the parotid saliva. Saliva samples collected by placing an absorbent sponge between the check and the molar teeth of the upper jaw with forceps. The sponges should be held in place for 1-2 minutes then removed and placed in a sterile container.

Ruminants attempt to maintain the total Na plus K concentration of the parotid saliva at 150 +15mmol/l in cattle and 180 + 15mmol/l in sheep. In the Na replete animal the Na concentration greatly exceeds that of K, but as the animal becomes increasing Na defi cient the Na concentration falls while the K concentration increases to maintain total ionic strength. However, as the animals Na defi cit grows the fall in Na exceeds the increase in K concentration and the total Na plus K concentration may fall by around

Table3.2:

Tentative criteria of Na status of cows from Na and K concentrations from the parotid saliva glands

NaStatus ClinicalSigns Salivacomposition Nammol/l Kmmol/l Na:KRatio

Suffi cient None >130 <13 >10.0Possibly insuffi cient None 87-130 13-38 2.3-10.0Insuffi cient Sometimes 43-87 38-64 0.7-2.3Severe Defi ciency Always <43 >64 <0.7

20%. Below 130mmol/l Na the animal fi rst tries to maintain Na status by reducing the loss from the kidneys. As Na defi ciency increases the Na levels can fall to <70mmol/l at which time we see clinical signs developing. It should be noted that within any group of animals a wide variation occurs in individual Na:K ratios and that at least 15 animals should be sampled to ensure the test is validated.

A normal Na:K ratio in the saliva is greater than10.0. A ratio below 10.0 indicates the Na status is insuffi cient. Unfortunately this test is diffi cult for a farmer to undertake and must be done by a veterinarian.

A normal Na:K ratio in the saliva is >10.0. Below 10.0, Na status is insuffi cient. Unfortunately this test is diffi cult for a farmer to undertake and must be done by a veterinarian.

The following table shows saliva Na and K concentrations and their respective ratios taken from Mike O’Connor’s Salt Drenching Trial in 2000 (14). The table highlights the low Na:K ratio’s in the milking cows that were not receiving salt supplementation.

Table3.3

M. O’Connor - Waikite Valley Salt Trial

Use of Salt in New Zealand Pastoral Farming Sodium in New Zealand Pastoral Systems

CowTagNumber DrenchedwithSalt Salivacomposition (YesorNo) Nammol/l Kmmol/l Na:KRatio

281 Yes 139.7 5.2 26.9279 Yes 145.4 7.6 19.1253 Yes 138.4 8.7 15.991 No 85.6 37.9 2.3298 No 110.1 34.4 3.2116 No 121.9 20.4 6.0Average for SaltDrenched Cows Yes 132.2 10.5 12.6Average for NonDrenched Cows No 105.9 30.9 3.4

TopdresingPastureswithSalt 4.0

• SoilNaquicktest<5requiresfurtherinvestigation.PastureNalessthan0.1%isdeficientformostgrazinganimals

• FertilizingpasturescontainingnatrophilicplantspeciesiseffectiveforraisingplantNalevels

• Recommendedsaltfertilizerapplicationis100kg/ha/annum

• Beawareofinteractionswithotherminerals• MonitorsoilandpastureNa

Sodium (Na) is not required for plant growth but is essential for animal health and production. One way of providing Na to animals is to topdress pastures with salt. Topdressing with salt will increase the Na content of pastures and provide Na to the animals grazing those pastures. However, not all pasture plants will take up Na (see Chapter 2 for a description of natrophobes and natrophiles) but the common pasture plants like ryegrass, white clover, cocksfoot, Yorkshire fog and phalaris are all capable of absorbing more than 0.1% Na into their leaves.

Background 4.1

Sodium deficiency is likely to be more common in inland areas away from the sea (see Chapter 3). Recent estimates suggest 20% of New Zealand dairy farms and 5% of sheep farms could be deficient. Dairy farm figures could become even higher in future as on-farm nutrient balances suggest Na is in negative balance (- 12 to -14 kg Na/ha/annum) on most dairy farms (table 3.1). Rainfall is the major source of Na and leaching is the major loss.

DiagnosingNadeficiency 4.2

SoiltestsOf the exchangeable cations in the soil (Ca, K, Mg and Na) Na is normally present in the lowest concentration. Using the MAF Quick Test (the test supplied by the major soil testing laboratories in New Zealand) a sodium value of < 5 units in a soil sample suggests that soil Na levels are low. What needs to be done then is to confirm that Na is deficient in the pasture using chemical analysis.

PasturechemicalanalysesPasture samples should be taken from representative paddocks across the farm and sent to the laboratory for major element analyses including Na. Care needs to be taken in the

sampling process in the field-the person taking the samples needs to wear plastic gloves to ensure the pasture sample is not touched by bare hands (there is salt in sweat); the sample needs to be representative of what is growing in the paddock and being eaten by stock and it needs to be as clean as possible and not contaminated by mud or dust. Soil contamination will give a false Na reading. Getting a correct Na reading can be difficult hence the care needed in the sampling process.Interpreting the pasture analysis: if the Na value is 0.10% or less in the herbage Na deficiency is likely in the animals grazing those pastures.

Topdressing Pastures with Salt

Salttopdressing 4.3

Fertilizer grade salt (as supplied by Dominion Salt) is available from fertilizer companies and rural merchants. It can be readily mixed with fertilizers other than nitrogen. Mixing is best done by the fertilizer companies. Salt purchased for topdressing should be stored under cover and used soon after receipt. Prolonged storage of salt in damp conditions tends to make it go hard and lump, making application through spreading gear very diffi cult.

RatesandfrequenciesofapplicationField trials on rates and frequencies of application of salt to pasture have been undertaken in the past in a number of areas. Results suggest that rates of salt application mirror those of muriate of potash. A trial series in the Waikato in the late 80’s (15) concluded that an annual rate of salt application of 100 kg/ha was recommended. This rate lifted Na levels in the herbage 2-3 times above the critical level and maintained them there for at least 30 weeks(see below). There was no effect on pasture production. A rate of salt application of 50 kg/ha lifted Na levels in the herbage above the critical level but only for a short period of approximately 6 weeks. Rainfall was approximately 1300mm/annum in the Waikato situations. Where areas have very low annual rainfalls (less than 600mm) the 50kg/ha rate of application may suffi ce.

In situations where K is defi cient (and this could be farms which have intensifi ed in recent times)

salt (Na) application can substitute for K (16) to a limited extent and benefi t pasture production. These situations are likely to be rare as the normal practice would be to apply muriate of potash fertilizer.

Increasesin%Nainpastureanditsduration.When salt is applied to pastures it dissolves rapidly and is taken up quickly by plants. An indication of the increase in pasture % Na from different rates of salt application is shown in a fi eld trial on a pumice soil conducted by MAFTech in the late 1980’s (Table 4.1). The pasture was defi cient in Na to start with (the critical level for animals is 0.10 % Na). Six weeks after salt application % Na had increased up to the highest rate applied but by 30 weeks had fallen across all rates. However, with the exception of the 50 kg rate, % Na was still above the critical level. Similar increases were observed in soil test Na status with the 100 kg rate effectively raising soil Na level from 5 to 13 at 6 weeks then falling back to 8 at 30 weeks.The recommended salt application rate to lift and maintain % Na in the herbage is 100 kg/ha/annum. Lower rates, although useful for an initial lift in % Na in the pasture, will not last for more than 6 weeks. No appreciable benefi t is obtained by applying higher rates.

Table4.1

Effect of applied salt on the % Na content of pasture and its duration on a pumice soil near Putaruru

kgsalt/ha 50 100 200 400

%Nainpasture

At start (Sept) 0.07 0.07 0.07 0.07After 6 weeks 0.15 0.23 0.24 0.3430 weeks 0.11 0.15 0.16 0.21

EffectsofotherelementsWhere salt is being applied as part of a pasture maintenance fertilizer programme it can be mixed in with other fertilizers like superphosphate, potassic superphosphate and serpentine super. It should not be mixed with N fertilizers like urea or DAP. If there is any depression in K, Ca or Mg contents in herbage as a result of applying salt is likely to be relatively minor and unimportant at 100kg salt/ha. However, in situations where there may be a defi ciency of Ca, K or Mg the application of salt could make the situation worse for those elements. These situations can be easily averted by applying appropriate fertilizers or by ensuring animals are given the appropriate mineral supplementation eg. Ca or Mg.

MonitoringRegular soil testing of the farm every 2-3 years should highlight any downturn in soil Na status. Once levels reach 5 or less then pasture monitoring should be done. As explained above care needs to be taken in taking pasture samples to prevent contamination. If remedial action is being taken, ie. salt is being applied as a fertilizer, then pastures should be sampled annually prior to fertilizer application. The aim should be to raise the Na status of pastures above the critical level of 0.10 % Na (preferably

to around 0.15% Na or higher) and maintain this level throughout the year. Timing of sampling soil or pasture for Na status is not important although for annual monitoring purposes sampling should occur around the same month each year. This will ensure pasture composition, namely the proportion of grass/ clover/ weeds is about the same. Remember with pasture monitoring you are trying to analyse the Na content of what the animals are eating and this can vary amongst the pasture components.

FertiliserandlimeeffectsonpastureNastatusPotassium and lime can depress the Na status of pastures. This is simply due to K+ or Ca++ increasing and Na+ needing to reduce to maintain ionic balance in the plant. Potassium applied at 100 kg K/ha or more can depress Na status by 30-40%. This will have implications if the Na status is already in the marginal range. The potential for lime to do the same is present although in practice Mg++ seems to be the element most likely to be depressed by Na and K applications.The advice is to always be aware of the interactions which can occur when different fertilizers and lime are applied to pastoral land. Any effects will be most pronounced in the 6 weeks following their application.

Use of Salt in New Zealand Pastoral Farming Topdressing Pastures with Salt

Somedetrimentaleffectsofsalt 4.4

PastureburningRecommended applications of salt (up to 100 kg/ha) will not burn pastures. Rates higher than 100 kg/ha have the potential to burn. The burning effect is similar to that experienced sometimes when potash is applied at similar rates. It is a temporary setback in pasture growth which will recover once rain occurs.

SalinationeffectsonsoilstructureLarge parts of Australia and other dryland continents suffer from salination. This occurs when salt crystallizes out as result of hot, dry conditions over long periods of time. These are extreme conditions. The resulting land is useless for agriculture as it forms a deep crust of salt across the landscape. The closest NZ gets to areas of salination is in small areas of Central Otago. Where the problem is not too serious remedial action can be taken by irrigating the land and allowing salt to leach out of the soil profile.

TidaleffectsofseawaterThis can be a problem where you have tidal flats being used for agriculture. Northland has a number of these areas. The problem is that seawater containing salt replaces the groundwater. Some plants are more tolerant of salty water than others. The first approach to growing pastures on such land is to prevent the ingress of the seawater by building permanent weirs. Thereafter normal rainfall will gradually leach Na from the soil and it can be used for pastoral agriculture. Excellent pasture production can eventuate on such land. Plant species which tolerate saline soils are strawberry clover, tall fescue, phalaris, balansa clover, lucerne, annual medics and barley.

ApplyingeffluentshighinNaThere are a number of examples of effluents being recycled back onto land. Many of these contain high concentrations of Na. These include dairy factory effluents, paper mill effluent, human sewage effluent, meat works effluent and various other processing effluents. Often the main source of Na is from wash waters used to clean processing equipment. All these effluents can be useful sources of nutrients for pastoral production. The problem comes when application rates get too high and/or the soil types are not suited to land application. Often soil structural breakdown occurs as a result of very high Na inputs. Rates of 800 - 1000 kg/ha Na (up to 2500 kg salt/ha/year) are not uncommon.Such schemes need very careful planning, the right soil type (free draining)and most importantly careful management to be successful.

ExamplesofsaltuseonpasturesThere are various mixes that have been tried. These include applying fertilizer grade salt alone, mixing salt with normal fertilizer, substituting a portion of the potash in potassic superphosphate with salt, mixing a dusting grade salt with MgO for dusting onto pastures.

It should also be mentioned that a way to complement natrophobic pasture species (which do not take up Na) is to plant companion natrophilic species such as chicory or plantain. Salt can then be applied for uptake by the companion species. Other examples of this include lucerne sown with phalaris and kikuyu undersown with ryegrass.

SaltSupplementsforLivestock 5.0

• Saltisavailablewithorwithoutminerals,looseorpressedintosaltlickblocks,orasrocksaltimportedfromtheNorthernHemisphere

• Saltisaneffectivecarrieroflesspalatableminerals• Summitsaltblocksweatherataslowerratethanrocksalt• Gettingaknownamountofsaltintoeachanimalonadailybasis(eg.

drenching)isbestbutoftenimpractical• Offeringfree-choicesaltyearroundwillenableanimalstosupplement

theirneedsasrequired• Becautiousaboutrelyingonfree-choicemineralizedproductstocorrect

forclinicalmineraldeficiencies

Use of Salt in New Zealand Pastoral Farming

RangeofProducts 5.1

In New Zealand a wide range of salt based products are available for direct supplementation in animal diets. Some are used to increase sodium intake only while others use salt as a carrier for less palatable minerals. A number of products have been designed to provide daily requirements for sodium and selected minerals. Salt, with or without added minerals, is available loose, pressed in a salt lick block, or as mined rock salt from the Northern Hemisphere.

Salt. 5.1.1

New Zealand salt is solar evaporated salt from the sea. It is available in different grain sizes. When feeding stock and making up brines for water treatment use refined salt as this will contain minimal insoluble contaminants that can block water lines. Brines for water treatment systems can be made from fine or coarse salt - fine salt will dissolve faster than coarse but it is recommended that the mixing tank has mechanical stirring. When mixing salt with other minerals or feeds choose a grain size that is easily mixed with the other ingredients - this will reduce separation of salt from the other ingredients and reduce waste.

SaltwithMinerals. 5.1.2

There are numerous salt mineral mixes on the market with appropriate usage instruction. Salt inputs will vary depending on whether the salt is added as a filler, added to make the mineral mix more palatable, or added to supply a minimum daily sodium dose to the diet. Mineral mixes can be fed on their own with stock having free access as required, or added to feeds. Mineral balancers containing salt are available for specific low sodium feeds like maize. Soluble

mixes are available for water treatment systems and drenching. Usage instruction for the animal class should be followed to avoid over or under dosing.

SaltBlocks. 5.1.3

Salt and mineralized salt blocks are readily available throughout New Zealand. Placed on the ground or in a purpose-built salt block holder, stock have access to the blocks as required. Individual animal intakes will vary depending on need - the highest producing animals are likely to require more salt. Salt blocks can be left out year round. Salt is very soluble so salt blocks will weather. In high rainfall areas protecting the block from rain is advisable. MineralisedSaltBlocks.Although salt contains minor quantities of other minerals these are not significant enough to contribute to daily requirements. The addition of minerals, especially trace minerals cobalt, iodine and selenium, can enable significant intakes to come from salt blocks. Flavour enhancers such as molasses are often added to improve palatability and ensure regular intake of the block (and the minerals it contains).

“Byaddingmineralswhicharelackinginsoilandpasture,stockareabletobetrickle-fedtheseinthesaltblock.Inourcasespecialemphasisisplacedoniodine,zincandselenium”-MarkUrquhart,GraysHills

“AtForestRangewehaveovermanyyearscorrectedawidespreadsodiumdeficiencywithsaltblocks.Theapplicationshavebeenregularandarestrategicallyplacedforstocktoutiliseinahighcountryenvironment.

Alsoofimmensebenefitarethetraceelementsthatareavailableinthisproduct.TheseSummitLittlixareappliedwithahelicopterandan‘Airmecapplicator’whichdischarges50blocksintendumpswiththeflickofaswitch.

Wehavealsotopdressedsaltontopaddocksatratesvaryingfrom100kgsto700kgsperhectarewithsomeverysatisfiedstockandnoproblemswhatsoever. SodiumandtraceelementsupplementationisaroutineexerciseforourUltraFineMerinosandanimportantaspectofouranimalhealthprogramme.”RS&JEmmerson,Tarras RockSalt. 5.1.4

There are no deposits of rock salt in New Zealand, in fact, there are very few in the Southern Hemisphere. Rock Salt deposits were formed underground about 150M years ago and mining them is carried out in a similar way to coal. Rock Salt is often coloured with minor quantities of minerals but as is the case with

other types of salt these minerals are usually not present in enough quantity to significantly contribute to daily intakes, even if what is present is readily absorbed.RockSaltWeathering.In 1990 AgResearch conducted trials on block weathering at Tara Hills and Ruakura Research Stations. For a number of years farmers had been claiming that rock salt weathered at a slower rate than pressed salt blocks. When Dominion Salt developed Summit Rock Block as a longer lasting product its weathering rate was tested against imported rock salt. The results were conclusive - Summit Rock Block showed a markedly slower rate of erosion/weathering when compared to imported rock salt. At Tara Hills Summit Rock Blocks lasted 1.8 times longer when exposed to weathering elements. Salt blocks can weather better than rock salt but this will depend on their composition and processing. Although not tested, differences in disappearance of rock salt and salt blocks in a paddock may result from palatability issues.

Table5.1

Salt block and rock salt weathering rates

SaltBlockWeathering,TraaHills1990/91

0Days 100Days 200Days 300Days

%o

fBlo

cks

Rem

aini

ng 100

80

60

40

20

0

ImportedRockSalt

SummitRockBlock

Use of Salt in New Zealand Pastoral Farming Salt Supplements for Livestock

IndicationsforUse 5.2

FreeChoiceSalt 5.1.5

Animals have a strong appetite for salt but individual salt needs will vary. Factors infl uencing salt needs include:• Sodium and chloride levels in the pasture • Sodium and chloride levels in the water• The production cycle - growth, lactation and

reproduction will increase requirements• Temperature and/or humidity - sweating can

increase sodium requirements• Sodium levels in supplementary feeds• Potassium levels in the diet

Offering free choice salt year round will enable animals to supplement their needs as required. Where mineralized products are offered free

choice mineral intakes will vary according to salt needs. Free-choice mineralized salt products should not be relied upon on their own to correct for clinical mineral defi ciencies. Adequate supply of stock drinking water should always be available when stock have access to free choice salt.

“Saltblocksareusedsporadicallythroughouttheyeartoprovideafortifiedmineralformula.Theformulawasadjustedovertwoyearsagotocomplementthedrenchprogramme,supplementaryfeedprogrammeandgrazingprogrammewhichincludesahighercontentofLucerneandforagecereals.Itislikelytheformulawillchangeastheflockdevelopsandnewideasandpossibilitiesarise...”-SnowLoxton,SawdonStation

There are a number of options available for correcting low sodium intakes. Getting a known amount of salt into each animal on a daily basis (eg. drenching) is the best option but often impractical. To meet the changing sodium needs of individual animals, access to free-choice salt year round will provide a useful backstop.

Table5.2

Indications for types of salt use in pastoral farming

Limit Fertilize Drench AddSaltto AddSalt Free-choice Test withSalt withSalt Wateror toFeed SaltLicks Supplement andBlocks

Soil <5 Na Min. 100kg/ha As required quick test) Annual application

Pasture <0.12% Na DM, 35g salt/ 35g salt/ 35g salt/ As required Lactating Cow cow/day cow/day cow/day

<0.10% Na DM, Up to 10g Up to 10g Up to 10g As required Beef Yearling salt/head/day salt/head/day salt/head/day

<0.08% Na DM, Up to 5g Up to 5g Up to 5g As required Sheep salt/head/day salt/head/day salt/head/day

Supplementary <0.25% Na DM - Up to 25kg salt As requiredFeeds all animal classes /tonne of feed

SpecificApplications 5.3

• For pasture fed dairy cows the critical Na level for supplementing with salt is 0.12% DM

• Salt can be applied in fertilizer, as a drench, in water treatment systems, added to supplementary feeds or offered free-choice in the form of licks

• Getting a known amount of salt into each animal on a daily basis is best eg. drenching

• The economics of supplementing with salt where there is a know Na defi ciency are signifi cant. For the Waikato Valley trial at 2007 prices, for every $1 spent on salt the return is +$50 in additional milk

Methodsofsaltsupplementation 5.3.1.1

Salt can be given to dairy cows in various ways. All methods have their place.

DrenchingDrenching is seen as perhaps the most appropriate method for milking cows. One can be sure all cows are receiving the same dose and the rate can be varied according to their production. Recommended salt dose rates are shown in Table 5.3. (as calculated from Towers and Smith, (7))

Table5.3.

Salt dose rates according to cow liveweight and production.

Liveweight Milk gNa/day gsalt/day kg kg/day

Lactation 450 10 10.0 25 20 15.8 40 30 22.3 56Maintenance 450 - 3.0 7.5

It is important if Na defi ciency is diagnosed to use the correct rates of salt as indicated. Lower rates will not provide the full benefi t. In the Rotorua trial mentioned below the farmer’s cows were given half the recommended dose rate. As a result they produced half the milk of the salt drenched trial cows.

Salt dissolves easily in hot water and can be mixed with other materials like bloat materials, magnesium compounds and trace elements.

WatertreatmentThis method is widely used in water troughs and automatic dosing devices for supplementing animals with salt. It is appropriate for situations where there is only marginal Na defi ciency or where the farmer feels salt may be benefi cial. Other additives can be added also. The downside of water treatment is that not all animals drink the same quantity of water on a daily basis so the salt intake can vary between animals. It is also possible to overdo the rate (especially for water troughs) and make the water too salty to drink. Nevertheless the method is convenient to use and will provide salt to animals.

Use of Salt in New Zealand Pastoral Farming Salt Supplements for Livestock

BlocksandlicksBoth have a convenience factor associated with their use but like water treatment individual animal salt intake is not guaranteed. Again the salt can be available along with other additives like trace elements and magnesium.

PasturetopdressingSalt is often mixed with other fertilizers like superphosphate or potassic superphosphate. This is done by all the fertilizer companies. It should not be mixed with N fertilizers like urea as it can cause caking and be difficult to spread. Salt is taken up quickly by pastures. In this way it is similar to potassium. In general terms 100 kg/ha/annum of salt will lift pasture Na levels appreciably and prevent Na deficiency in grazing dairy cows (see Chapter 3). Some plants (natrophobes) will not take up Na to any extent. Lucerne, kikuyu and browntop are examples of natrophobes. However typical ryegrass/clover pastures in dairying situations will take up Na satisfactorily. Pasture topdressing is again a convenient method of providing Na to cows. It is important that the rate is not compromised if pasture Na levels are to be maintained throughout the year. In some instances where pasture K levels are high the fertilizer mix can be lowered in K and increased in salt.There have been instances of Na reducing pasture Mg content and causing grass staggers. This will not be a problem where adequate Mg supplementation is practiced.It should also be noted that supplements like maize silage need to have salt added at feedout as the pasture will not provide sufficient Na for this purpose.Pasture dusting with salt (and Mg) is another useful way of getting salt into dairy cows in late winter/ early spring. The salt adheres to the leaves and is eaten by the cows.

Recentdrenchingtrialresults 5.3.1.2

WaikiteValley,Rotoruatrial(14).In 1999/2000 a trial was conducted in Waikite Valley, Rotorua (property of Jim and Dorothy Rotheram). 90 cows from the herd were grouped into 45 pairs based on breed, age, calving date and milk production. One group was drenched with 35 g salt/day the other group left as an undrenched control. Fortnightly milk production was measured using the LIC Herd Testing Service.The pasture on 5 paddocks was sampled monthly and analysed for % Na. The farm water supply was tested for Na content.Milk yield responses. Over a 3 month period milk production increased by 12.8% - a statistically significant increase. The production increase occurred within 2 weeks of commencement and continued for the 3 month duration of the trial. Milkfat and protein content. There was no effect on milkfat or protein in the milk over the duration of the trial.Pasture Na status. Pasture samples were deficient in Na averaging 0.05% Na over the 3 months of the trial. Saliva Na: K ratios. Saliva Na: K ratios of the drenched and undrenched cows was measured towards the end of the trial. The undrenched cows had a ratio of 16.8 the drenched cows 6.7. This aspect is discussed further in section 3.3.2.

“..havenotstoppeddrenchingwithsaltsincethosetrailsbecauseofthevastimprovementweachieved”-JimRotherham,WaikiteValleyDairyFarmer

Ruakuratrial,No2Dairy(17) A trial with 188 cows on 10 armlets was conducted in January/February 2001. Cows were allocated to a salt drenched or control

group on the basis of age, genetic merit and milk production. Stocking densities on the 10 farmlets differed. Again cows in the treated group were given 35 g salt/day.Milk yield responses. There was no benefit in milk production over the duration of the trial.Milkfat and protein content. No effect noted.Pasture Na status. Pasture samples collected twice over the trial period averaged 0.10% Na.This trial allowed very close monitoring of cow intake and Na intake /cow/day. In all cases the Na intake from pasture indicated that a Na content of 0.10% in pasture was sufficient. This occurred where cows were fed either ad libitum down to 66% of cow requirements.

CriticalpastureNalevelsfordairycowsOverall these two trials have indicated that pasture Na status less than 0.10% Na is likely to be deficient in Na for high producing dairy cows. A value of 0.10% Na in one trial gave no response; a value of 0.05% in another trial gave a 12.8% response in milkfat production. As indicated in Table 5.3 a safe optimum would be 0.12% Na in pasture. Pasture composition may be important at times with various herbs like chicory and plantain being high in Na. Nevertheless these need to be present in high amounts or as special purpose pastures to really influence Na intake to any extent.

OthersourcesofsaltAnimals can obtain salt from ingesting soil. This may be involuntary as soil or dust contamination on leaves or voluntary as in licking banks or wooden fixtures. Water supply is an obvious source of Na. Na concentration will be dependent on the source of the water and the geological status of ground from where it comes. Salt on fence posts, fence wire and other fixtures is likely to be rain borne and is

particularly prevalent near the coast .Again animals can be seen licking such fixtures. Remember that the sight of animals licking such structures does not mean they are necessarily deficient in salt. Animals and humans like the taste of salt. Proper diagnosis of deficiency as outlined in section 3.3 is necessary as a basis for treatment.

EconomicsofsaltsupplementationWhere Na deficiency is diagnosed and applying the Rotorua trial response figure of 12.8% a cow producing 350 kg milk solids (MS) would with salt supplementation produce an additional 45 kg MS. At $6/kg MS this would equate to an additional $270/cow income. The additional costs entail 35 g salt/cow/270 day lactation or 9.45 kg salt/cow. With drenching grade salt at 50c/kg or $4.73/cow, plus any additional labour costs, drenching would still give a very economical outcome.

CautionswithsaltsupplementationThere have been instances of salt drenching causing contraction of the oesophageal groove in dairy cattle. It is then possible for salt and any bloat additives to bypass the rumen and end up in the abomaseum causing the animal to suffer a bloat attack. This is seen as a very rare occurrence (18). The rate of salt addition may need to be reduced in such situations. (refer also to section 7.1)Salt can be detrimental to animals given in excess. Toxic animals display a nervous disposition. It is important to ensure an adequate water supply is available at all times.

“....animalsneedsalt...SummitAmaize(mineralbalancer)issprinkledovermaizesilagewhichisfeedintoughsonafeedpad.Multimineralsaltblocksareavailableallyearroundonthefeedpadaswell.”-PeterSpreeuweenburg,DairyFarmer,Ngatea

Use of Salt in New Zealand Pastoral Farming Salt Supplements for Livestock

BeefCattle 5.3.2

• Cattle on low Na diets respond to salt supplementation

• Use salt blocks when feeding lucerne and other natrophobic plant species

• Pasture Na 0.1% DM is adequate for beef cattle production

• Salt can be used to manage grazing intensity and location

Many studies have been carried out overseas, particularly in USA, on the “Role of Salt in Animal Nutrition”. Dr Larry Berger (19) reports that feed represents about 70% of the total cost of beef production and numerous studies have shown that sodium chloride supplementation is an essential part of a balanced diet required for efficient beef production. In Kansas State studies (20), calves that were self fed salt, gained twice as much as those not receiving any salt and they consumed more total daily feed. In another study, steers fed salt gained 29kg more than those without supplemental salt over a 327 day period. In a 1971 trial (21), steers on full feed consumed more feed but gained approximately 23kg more than steers not receiving salt. A 1973 Australian report (22) showed that salt supplementation significantly increased the gains of lactating beef cows and their calves while grazing native pastures.

In New Zealand studies have been carried out on cattle feeding low sodium diets. Sodium supplementation trails were conducted between 1974-1975 by Dr. J.P. Joyce (23) at Wairakei Research Station, Taupo, using beef cattle. In each of the two indoor trials, groups of five cattle were fed freshly harvested lucerne which was supplemented with 200g NaCl per day (15.7g Na/animal/day), sprinkled over their feed. In the first trial lasting 84 days from January - April

and using 5 month old Angus weaner heifers weighing 130-140kg, those fed to appetite plus salt gained liveweight 48% faster than the control animals. In the August - March trial, using 12 month Angus steers weighing 200kg, the liveweight gain was 16% faster. Dry matter intakes of NaCl supplemented cattle were 3.1% and 8.6% greater in the 1974 and 1974-75 trials respectively, than the comparable control cattle, suggesting gains came from increased appetite and better feed conversion. At current (2007) rates the salt input would cost 2 cents/head /day and the carcass weight gain would be worth 18 cents/head/day. In both trials, growth rates during the summer period were extremely low.

A salt block supplementation trail was conducted in 2001/2002 on a large grazing property in the Taupo district using mobs of dairy heifers (24, 25). The study investigated the performance of salt blocks on a low herbage sodium site on cattle liveweight gain during the spring/summer period. Two mobs of 100 dairy heifers were offered salt blocks ad libitum for the duration of the trial and two mobs had no access to salt blocks.

Results were not conclusive. While there was a significant response in liveweight gain to salt over the period January to February, it was only with one of the two salt supplemented mobs of dairy heifers. Over the trial period (5 months) for the mob that responded the salt blocks cost $7/head and the extra carcass weight was estimated to be worth $34/head. There was no trend for the period October to January.While the herbage sodium levels were low, particularly at the commencement of the trial, pasture dry matter on offer was high throughout the trial. Herbage intake for the liveweight gains were measured and the sodium requirements were met by this level of herbage on offer, without the need for salt supplementation.

The result may have been different if dry summer conditions prevailed and pasture quantity and quality was reduced.

“Saltblocksmaybeacheaperalternativethanmixingsaltwithfertilizerbecauseofmixingissues,particularlyifnitrogenisbeingusedinthemix”Farmer

Animal behaviour was observed in this trial. The grazing rotation of each group resulted in the same paddocks being grazed by the control

and salt mobs at different times. It was observed that the control mobs sought out the areas where salt had been available in troughs to the salt mob, to the extent that holes were dug in the soil presumably to find the salt (Figure 5.3). Animals are often seen licking fence posts, rails and concrete structures, to obtain their sodium requirements. However, at the trial site, calves were not seen chewing rails so readily which may reflect weather conditions and the higher availability of sodium in the pasture diet.

Figure5.3.

Control animals searching for salt

EstimatedNarequirementsofcattleThe Na requirement for beef cattle depends on their weight and growth rate. Lactation lifts Na requirements even higher. From Table 2.2 a 200kg steer growing at 0.5kg/day will have its Na

requirement met by pasture offering Na at 0.07% DM. For a lactating cow the Na requirement is 0.12% DM. Towers and Smith (7) suggest Na requirements for cattle will be met if pasture contains Na 0.10% DM.

NEWPIC-TOCOME

Use of Salt in New Zealand Pastoral Farming Salt Supplements for Livestock

SaltingrazingdistributionBecause beef cattle have a strong appetite for salt, it can be used as a management tool as well as a source of nutrient. For example, salt blocks can be used to increase the carrying capacity on pastures by causing more even grazing. On areas where less palatable forage is available, salt blocks distributed over those areas will encourage more even utilization (22). (See section 6.1 also)

FeedlotsWith feedlots becoming more common in New Zealand, the use of salt becomes an important consideration. A salt deficiency can cause cattle to choose an imbalanced diet in order to get additional sodium or chloride. When this occurs, animals may eat more supplement containing higher sodium concentrations, thus increasing the cost of the feed (26). It is important to have balanced diets and these can be made up to go through the mixer prior to feeding out on the pad or in troughs.

High concentrations of salt have been used to regulate feed intake, particularly overseas, in a range of situations. In New Zealand, it is more applicable to feed lot situations. While the science of using salt to regulate intake has been well researched, the ‘art’ of using this technology is still developing. A clean, plentiful water supply is a must when using salt to control intake

“Wehavealsousedthem(saltblocks)inattemptstosealdams.i.e.buildastockwaterdamwithadiggerorbulldozerandputsaltblockinbottomsostocktrampleandsealthegroundsothedamholdswater.Worksbestwithbigmobsofcowsandcalves.”-JohnFord,sheep&beeffarmer,Rotorua

SHEEP 5.3.3

• Sheep and lambs on low Na diets respond to salt supplementation

• Use salt blocks when feeding lucerne and other natrophobic plant species

• Pasture Na 0.1% DM is adequate for sheep production

• Measurement of Na deficiency in grazing sheep on commercial farms is not very practical

• Care should be taken when offering salt to severely Na deficient sheep to prevent smothering

• Salt can be used as a tool in grazing management

Many sheep and beef farmers will have been faced with the dilemma of whether or not to put out salt for their stock.

They may have put it out in the past because stock seemed to want it, but the introduction or reintroduction of salt has resulted in craving and stock losses through smothering. While opting for a constant supply of salt can reduce this problem, the expense and logistics of continually feeding stock with salt persuades some to stop using it. This is reinforced by the fact that after removing salt from the diet there is no obvious or apparent detrimental affect on production.

MarlboroughTrialsA trial (27) undertaken on Marlborough hill country establishing the effectiveness of small (2.5kg) salt blocks in reducing the incidence of smothering also showed several production benefits. Trial ewes had access to salt blocks from 3-4 weeks pre-lambing until tailing. The results included: -

• a significantly greater weight gain (10%) in ewes between tailing/docking and weaning. This coincided with the period when all ewes were run together without access to salt. This perhaps indicates that previous access to salt may be an important component of live weight gain. There was also some suggestion that there was a carry over advantage to those that had access to salt, in terms of body Na levels, for they maintained higher urinary Na levels at weaning 2 months after salt removal. As weaning weight in dry summer environments can be a good indicator of the following tupping weights the importance for ewes to gain lost weight before weaning cannot be over-emphasized. While wool production was not measured in this trial other trials have shown sheep supplemented with salt, when sodium deficient, have produced more wool

• a trend towards more lambs tailed and weaned per ewe mated and lower lamb loss between scanning and weaning. There is much anecdotal evidence that the level of mis-mothering and cross- mothering is reduced when ewes have access to salt over lambing. Some farmers, especially stud breeders, believe that the amount of interference at birth by other ewes is reduced if they have access to salt prior to and over lambing. It is felt that salt depleted ewes are attracted to foetal fluids.

“Wefindatlambingthateweswithgoodaccesstosaltaremoresettledandmothertheirnewlambswell”-MarkUrquhart,GraysHills

“Wehavealsofoundtheproblemofthieving(ewesstealingothereweslambs)duringlambinghasalsodeclined(withaccesstosalt)”-DougAvery,LakeGrassmere,Marlborough

This argument is supported by one Marlborough high country farmer’s finding (Steve Satterthwaite, Muller Station) when in 1995 he split his mixed age twin bearing merino ewes into two mobs prior to lambing and gave one mob salt. At tailing those that had had access to salt tailed 154% while those without only tailed 127%. He repeated the exercise the following year but swapped the blocks with the treated ewes running in the previous year’s control mob block. Those that had access to salt still tailed 165% - 20% more than the controls.

• a trend towards greater weight of lamb weaned per ewe mated (approx 2kg) when ewes had access to salt. At a value of $1.45/kg live weight and over a 2000 ewe flock the advantage to the best salt treatment would be around $6000.

This trial clearly indicated that salt “deficiency” could affect production through its influence on ewe behaviour and lamb survival, milk production, and body weight recovery after lambing.

SaltwithnatrophobesThe Marlborough trials all took place on over-sown topdressed pastures. The response however is more likely to be even greater if stock graze pasture species that contain low levels of Sodium such as lucerne. Dr J P Joyce described in the 1975 Ruakura Farmers Conference Proceedings (23) the results of trials with weaned lambs, young beef cattle, and lactating dairy cows grazing lucerne. Salt treated lambs gained twice as much carcass weight (69 v 32 g/day) and (64 v 31 g/day) over untreated controls when drenched once weekly with 8.4g Na. In the beef cattle experiment (described in section 5.3.2) weaners fed to appetite gained liveweight 16% to 48% faster when supplemented with salt. They also consumed more feed. The dairy cows

Use of Salt in New Zealand Pastoral Farming Salt Supplements for Livestock

responded to salt supplementation with a 14% increase in milk production.

Another advantage of putting out salt blocks to sheep on lucerne is that the incidence of bloat amongst ewes and lambs has been observed to diminish once they have had access to salt (See Chapter 7).

RunningcowsandewesinthesameblockIt is also possible that salt deficient beef cows could respond in a similar manner to dairy cows when given salt with an improved milk production and hence calf growth rate. However of more importance could be the reduction in new-born lamb mortality through the interference with lambing by salt deficient cows when ewes and cows are run together. Salt deficient cows have been observed licking and sucking on newly born lambs - perhaps attracted to the salty taste of foetal fluids. This tendency stopped once salt was placed in the blocks.

“’Aschworthrunsonlymerinosheepandcattle.Theflockismadeupofmerinoewes,wethers,andmixedsexhoggets.Weruncowsandfattenallprogeny.Saltusecanbeputintothreegroups.Weusesalttwoweeksbeforeandthroughoutmatingofewes.This,Iamsure,hashelpeduswithaveryconsistentlambingpercentageoverthelastfewyears.Saltisagainusedseveralweeksbeforelambing.Thiscoincideswithcalvingandsaltenablescowsandewestorunonthesameblocks.SaltisalsousedonAschworthtodrawsheep,especiallywethers,ontoun-grazedpartsofrougherblocks.

Littlerockblockisthepreferredsalt,especiallywhencattleandsheeparegrazedonthesamecountry.”TimandSallyWadworth,Marlborough

Testingforsodiumdeficiency.While it is always useful to know in advance whether or not supplementation of salt is likely to be beneficial or cost effective, testing is not altogether that easy or straightforward. The recommended test is to measure saliva sodium. However this test is time consuming, difficult to do well, expensive to analyse and subject to many possible errors and, except for research purposes, probably impractical in most situations.

Because of the variation in urinary Na output from different individuals at any one time, and the diurnal variation of any one individual under normal circumstances, urinary Na has not been accepted as a useful measure of a flock’s Na status. However when salt demand is high, measured by salt consumption, the urinary Na levels can be less than 1 mmol/L with very little variation between individuals. Only excess Na is excreted in the urine as kidneys are very efficient at conserving Na when the occasion demands. Urinary Na is therefore a useful indicator of sodium status when it is low. A mean urinary sodium concentration less than 3 mmol/L in a sample of 10 ewes would indicate sodium deficiency and the need to supplement. (7)

However probably the best determinant of a salt deficient mob is whether or not stock crave salt. Despite all ruminants being halotrophic (ie. they seek out salt whether or not they need it) it was noticeable in the trials in Marlborough that most salt was consumed on the trial properties that were the most deficient in soil and herbage sodium. Consumption of salt was also less where improved pasture species, especially natrophilic (sodium loving) ones such as ryegrass, cocksfoot and white and subterranean clovers become more dominant in the sward.

NarequirementsofsheepAlthough farmers are generally unlikely to feed salt to a level in excess of 0.5 kg/ewe consumption per ewe can be in excess of 1 kg/ewe on sodium deficient sites from a month prior to lambing and up until tailing if salt is freely available. Caution should be applied when offering salt to craving animals a few days prior to lambing (refer to section 7.2). The actual requirement for ewes at this time varies depending on body weight, whether she is carrying a single or twins and during lactation how much milk she is producing. For instance a twin bearing ewe in late pregnancy requires about 2g salt/day while during lactation may require up to 3.5 g salt/day. The maintenance requirement for a ewe is about 1g salt/day as is that of a 30kg lamb growing at 150g /day. Towers and Smith (7) suggest Na requirements for sheep will be met if pasture contains Na 0.10% DM. CautionsAs excessive intakes of salt are possible and can be toxic care must be taken especially when re-introducing stock to salt. Deaths can occur as a result of smothering if stock crave salt and the use of smaller blocks can go a long way to reducing this possibility. Access to a ready supply of salt can also be fatal if water is not freely available. High intakes of salt can also depress plasma Mg and Ca levels and may increase the risk of metabolic problems.

SaltasagrazingmanagementtoolThis attraction of stock for salt was the reason behind a FITT funded project in Marlborough in 2002-2004. A trial was done to determine whether the aerial application of a mixture of salt (100kg/ha) and molasses (130L/ha) and urea (40kg/ha) would attract stock to specific areas and whether it encouraged sufficient

extra grazing in the treated areas to reduce the amount of “tag” and form a fire break.

The areas chosen were usually the more unattractive poorly grazed areas with a high % of rank pasture. Nevertheless stock were attracted to the treated areas. Although pasture control was improved on these areas it is debatable whether the extra grazing pressure would have been effective in producing practical “fire breaks”. However better quality pasture did result after the treatments with more vigorous grass and clover and less dead matter. Pasture improvement being the result of both direct nutrient application from the treatments and an animal impact effect. The animal impact effect - trampling, urinating and defecating in a confined area, could be an effective means of introducing and getting new pasture species established and improving poor quality hill country pastures. OtherSpecies 5.3.4

Goats. 5.3.4.1

NRC salt feed recommendations for goats are the same as those for sheep. They note that “placing salt in less frequently grazed pastures may influence goats to move to these areas” (28). For goats grazing hill country with low soil Na offering free choice salt blocks provides a practical supplementation solution. Goats producing large amounts of milk will require higher levels of salt to replace Na and Cl lost in the milk.

Pigs. 5.3.4.2

Salt is an essential part of the diet for growing pigs. Studies in the USA showed that a deficiency of salt decreased daily gain and feed efficiency in the pig (29, 30). In one trial

Use of Salt in New Zealand Pastoral Farming Salt Supplements for Livestock

it was calculated that one pound of salt saved 185 pounds of feed. (31). NRC recommends, “that 0.2% to 0.25% sodium chloride will meet dietary sodium and chloride requirements of fast-fi nishing pigs fed a corn-soybean meal diet” (32). Salt poisoning is unlikely providing adequate water is available.

Horses. 5.3.4.3

The need for salt varies depending on the horses’ level of work, riding and heat stress. Sweat contains about 0.7% salt so the more a horse sweats the more salt is lost and the greater the salt needed in the diet. Free-choice feeding of salt is recommended to ensure adequate intake at all times. The use of electrolytes will also replace lost Na.

Poultry. 5.3.4.4

Salt defi ciency has the same negative growth effects in poultry as in other animal classes. Salt is not self-fed to poultry so their needs must be met by adequate levels in the diet. Commercial poultry feeds will include salt if the other feed ingredients are defi cient in Na.

Deer. 5.3.4.5

There is very little information available on salt requirements of deer . At times deer will take free-choice salt licks and blocks and at other times they will leave them alone for months. However, it should be assumed that deer have similar requirements for Na as sheep until experimental work indicates otherwise. Mineralised salt products, especially containing copper, are often made available free-choice to improve trace mineral intakes of deer.

SaltandSupplementaryFeeds5.3.5

Na and chloride are essential for all livestock and required on a continuous basis. Na is needed most during growth and lactation. Salt is critical for maximizing appetite and feed intake as well as for digestion of fi brous feeds and rumen pH buffering and function.

Sodium intake in NZ comes predominantly from grazed pasture. Many other strategic feeds are low in sodium. To maximize the benefi t these feed supplements provide to dairy production they need to be re-balanced for Na levels. It is critical that pasture levels of Na are known as that source usually makes up the largest proportion of the diet. Grains (maize, barley, wheat), palm kernel meal (PKM), coprameal, lucerne are generally low in Na. They are defi cient to the point where feed intake and rumen output will be limited if salt is not supplied to re-balance the diet.

Recent estimates suggest up to 20% of NZ dairy farms could be defi cient in sodium. Diets with palm kernel, grains and maize silage exacerbate this problem even further.

United States NRC (33) give minimum requirements of Na 0.2 - 0.34% DM for lactating dairy cows using sample diet models. Dry matter and milk yield responses to Na over the range of 0.11% to 1.2% were maximized at 0.7-0.8% Na in 15 trials referenced by NRC .

Somebasicrulesofthumb(fromGrantRichards,Nutritionist):When feeding high potassium pasture, low Na feeds (PKM, maize silage, grains) and highly fi brous feeds (NDF +40%), Na should be increased to ensure 0.4-0.5% Na on a DM basis

along with ample fresh and clean water. Increase salt to 5-10 grams per cow per day for every 1kg of PKM or maize silage being fed. For every 5% NDF rise in the diet, increase salt by 5-10 grams

Table5.4

is a guide for adding salt when using supplementary feeds. The minimum sodium of 0.25% is within the NRC range and the optimum range is conservatively based on the trials NRC has referenced.

Note:CalciumandmagnesiumarealsolowinmanyoftheabovefeedsthatrequirebalancingSalt (coarse and fi ne) can be added to the feed or top-dressed on feed pads. Higher levels of salt should be at least partially mixed in with the feedFor standing crops salt licks or salt blocks can be used. Ensure continual access to salt and water. Do not feed salt to transition springer cows unless advised by a professional expert.

FeedSource NainFeed ForvariousNarequirements Minimum Optimum Na0.25%DM Na0.5-0.8%DM

%inDM Salt/tfeed Saltg/cow/day Salt/tfeed Saltg/cow/day for2-4kgDM for2-4kgDM

Grains 0.01 7.5kg 15-30g 12-25kg 25-50gMaize silage 0.01 7.5kg 15-30g 12-25kg 25-50gPalm Kernel, 0.01 7.5kg 15-30g 12-25kg 12-50gPKMTriticale 0.02-0.04 7.0kg 15-25g 12-20kg 25-40gWhole Crop 0.02-0.14 4-7kg 10-25g 4-20kg 8-40gCerealLucerne 0.04 7.0kg 13-25g 12-20kg 25-50g (low Na pasture) for 16kg DM for 16kg DMPasture <0.12 2.0kg 30-35g 4-7kg 65-130g

per cow per day. Having a coastal farm should not preclude proper investigation into what cows really need given the Na defi ciencies present in so many strategic, non pastoral feeds.

Use of Salt in New Zealand Pastoral Farming Salt Supplements for Livestock

UseofSalttoInfluenceGrazingBehaviour 6.0

• RuminantsshowacravingforsaltwhichisproportionaltotheNadeficiencyintheirdiet.

• ThiscravingforNacanbemanagedtoincreasegrazingintensitybystrategicplacementofsaltblocks

• ortopdressingwithsaltatupto100kgNaCl/haonselectedareasoflargepaddockssuchas:-

-undergrazedareasofpasture -weeddominantsites -stockroutesthroughwoodyvegetation -areasabouttobeseeded• Saltaloneisunlikelytoachieveallobjectivesandshouldbeusedin

conjunctionwithadditionalsubdivisionandstockwater,fertilisers,mobstocking,herbicideand/orfireandreseeding.

UseofSalttoInfluenceGrazingIntensityinHillPasture 6.1

Salt is often used on some inland, salt deficient properties to encourage livestock into less favoured areas. This has been a successful strategy for keeping stock routes open and for the expansion of grazeable areas in difficult terrain. Suppressing fern and scrub by hoof and tooth may also be preceded by herbicide and/or fire.

Pasture seed will be trampled more effectively if high stocking rates can be applied to limited areas. Seed spread immediately before salt will generate high grazing intensity and enhance the treating effect. Fertiliser (P, S, K, Mo etc) spread with the salt will give the young pasture seedlings a competitive chance against resident vegetation. Legume species will benefit most from the pulse of fertilizer. When regrowth of the native vegetation allows, let the newly established legumes reseed in the first year. Cattle can be used to eat the mature high sodium herbage and help spread the legume seed further.The intensity of grazing on areas where salt is spread will depend on the relative Na deficiency of the rest of the fenced block/paddock and the intensity of Na craving by the livestock. It is therefore unwise to spread salt widely on properties where livestock are to be used as tools for development. Keep the class of stock to be used as workers at least marginally Na deficient. Place the salt only where you want the stock to graze more intensively. Clearly this technique must be done with care in relation to the potential danger of smothering sheep. To help avoid smother deaths severalmini salt blocks or rock salt lumps should be spread rather than a single large block. The frantic competition within the flock for a lick of salt is then dispersed over a wider area.

Apart from the smothering issue salt placement in a paddock requires some thought to get the most out of predictable livestock behaviour. While it is convenient to place salt near a gate or beside the track or on flat well grazed benches in a steep paddock, consider other options which can lead to improved control of scrub and/or rank grass in less favoured areas of pasture. Avoid placing salt near water troughs and especially not near streams. The extra livestock traffic and congregation will create mud and stream pollution.In hill country, livestock camp at the highest point in a fenced area. Fertility is transferred to those camps and they tend to be dominated by weeds (barley grass, mallow, thistles) or mat forming grasses such as Kentucky blue grass (Poa pratensis). On less steep areas away from the main stock camp, pasture is grazed intensively and with the extra nutrient returns in dung and urine a high quality sward normally develops. This effect is also seen on benches beside stock tracks in contrast to the steep banks between the tracks. In a lot of hill country the steeper mid-slope areas of each block tend to be neglected by stock and grass becomes rank, clovers are shaded out and low grazing pressure means there is little nutrient return from stock. Salt can be used to encourage animals onto these steep under-grazed mid-slope areas. See Figure 6.1 (34)

Use of salt to Influence GrazingBehaviour

Figure6.1

Sheep grazing plots one day after applying salt. Before application of salt the hill area was occupied by very few sheep but after application high numbers of stock grazed the area attracted by the salt

“Theplacementofsalt(blocks)inlessgrazedareasie.dark,coldfaces,canattractmorestocktothoseareasandencouragemorebrowsingbehaviourastheanimalstravelandeat”-MarkUrquhart,GraysHills

“Weusesaltblockstoholdthecattleontheflatsinwinterandtoattractcattleandsheepontothehigherslopesinsummer.”-MikeKing,MtAlbertStation

Fine salt rather than coarse is less easily eaten from the soil surface immediately after it is spread but both grades will attract stock. On small areas (eg 20m x 5m plots) the vegetation is decimated and up to 50% bare ground is created in a few days. (See Figure 6.2).

Figure6.2

The result of 2 days grazing on a salt treated plot at Mt Grand

In country prone to erosion this generation of bare ground is not desirable. Extreme effects on vegetation of frenzied salt seeking can be modified by adjusting the rate of salt application, the proportion of the paddock treated and the number of animals available to do the work. In general, spread fine or coarse salt at 100 kg/ha on a maximum of 10% of a paddock and use a stocking rate of at least 10 su/ha for several days. If all animals are drawn to the salt treated 10% of the paddock that would result in a grazing pressure of 100 su/ha on the salted area. In a subsequent year a new 10% of the same paddock may be treated if the pasture on the previously treated area continues to be grazed more intensively (34).

Precise aerial spreading of granular salt on mid-slopes is probably more expensive than putting out mini-blocks or rock salt. A problem with rock salt lumps is that stock worry them down hill towards scrub filled gullies and streams while brick shaped mini-blocks tend to stay put. A cunning trick to hold salt lumps and blocks on the mid-slope placement sites needs to be devised!The subtleties of using salt to influence grazing intensity in hill county involves several important variables and best practice needs to be developed for different properties integrating the following general issues:- 1. the degree of salt deficiency in the soil and

herbage.

Use of Salt in New Zealand Pastoral Farming Use of salt to Influence GrazingBehaviour

2. the intensity of salt craving of the livestock and their physiological state.

3. the ability to apply a high paddock stocking rate with an appropriate class of stock soon after salt is spread.

4. seasonal timing in relation to plant growth potential and livestock physiological state (eg pregnancy, lactation, etc).

5. influence of rainfall washing salt off herbage and into soil soon after it is spread.

6. the balance of natrophobic and natrophillic plant species in the pasture.

All the above issues feed into decisions on the proportion of large paddocks to be treated with salt and the rate and form of salt to be used. If pasture legume seed is to be broadcast then the optimum time for sewing seed has to be integrated with points 1-6.

Deer, chamois and thar appear to thrive in the New Zealand back country. Much of their natural range covers inland Na deficient environments. There are also some inland farms where little or no salt is used. Furthermore there appears to be no plant species with high Na content which is favoured by the wild ungulates and farmed sheep and cattle. Where do these animals get their Na?

“Mount Grand”, the Lincoln University farm at Hawea Flat, was an ideal property to study the behaviour of grazing animals in a Na deficient environment. It presented a dilemma; no salt had been used on Mt Grand for many years, all top soil QT values showed very low Na ranging between 1 and 3, and herbage on the hill blocks ranged between 0.02 for white clover and less than 0.01 for tall oat grass. Clearly it was a Na deficient environment but animal productivity

Livestock“saltmines” 6.2

was comparable to other farms in the district where salt is used. A clue towards solving the dilemma came with the observation that sheep seemed to regularly visit steep eroded sites where the subsoil was exposed. Closer inspection revealed sheep tooth marks where the subsoil was free of course schist grit (see Figure 6.3). Six subsoil samples were analysed. The 3 from shady sites had an average QT of 4 which was twice the Na in the top soil but still deficient. The 3 sites from the sunny face had 9, 28 and 57 QT Na. The site with57 came from the tooth marked face in the photograph. It can reasonably be called a sheep salt mine! It is therefore probable that Mt Grand sheep supplement their Na deficient pasture diet by ingesting subsoil on north facing banks where the Na content is much higher than normal soil.

Similar sites can be seen on many properties where animals congregate and contribute to the exposure of subsoils. It is possible that soil ingestion contributes Na to livestock diets from these sites. While animals can increase their Na intake by soil ingestion it is undesirable because of increased tooth wear and dust in wool. Also if large amounts of soil are eaten feed intake and hence animal productivity will be reduced (35).

Figure6.3

A Sheep Salt Mine

The use of salt blocks or salt fertilization of pastures are obvious solutions to reducing the need for livestock to eat soil.

“...Thosewithoutsaltalsoeatalotofsoil-thisishardonteethandgetsintothewool”-MarkUrquhart,GraysHills

Use of Salt in New Zealand Pastoral Farming Use of salt to Influence GrazingBehaviour

AreasofUncertainty 7.0Bloat, primary ruminal tympany or acute frothy bloat, is an important digestive disorder on many dairy farms in NZ. It can also affect sheep. Bloat occurs when the normal mechanism for eructation of rumen gas is inhibited or impaired. Under NZ farming conditions this eructation mechanism is commonly inhibited by the frothy rumen contents which trap the gas causing the animal to bloat. Rapidly digested, high protein forages cause the greatest risk eg. legumes (clovers, lucerne) and young lush leafy grasses.

Research on the workings of the rumen has provided the following observations:• Increasing rumen pH can reduce frothiness• Ruminal cations, Na+ and K+, and Mg++

and Ca++, are important and are correlated with bloat

• Low ruminal liquid clearance rates are observed in bloating animals

• Bloating animals have reduced feed intake• Rapidly digestible, high protein forages

increase the risk of bloat

So will salt eliminate bloat? Sodium has a role to play in buffering rumen pH (ref section 2.2). The theory suggests it may have a role to play but research experiments to date have failed to offer evidence that supports the use of salt to control bloat. Turner in 1981 (36) reported that a Na:K ratio of >1:20 in pasture may exacerbate bloat but Carruthers et al (37, 38) found no relationship between Na, K or Na:K in soil or pasture with the incidence or severity of bloat. In Canada, Hall et al (39) tested whether manipulation of cations through supplementation might provide a means of controlling bloat - their conclusion was that Na supplements were ineffective at preventing bloat. Farmer observations suggest that salt may be a useful tool in reducing bloat.

• Naisimportanttotheefficientfunctionoftherumenandthechangesthatoccurwithintherumenofbloatinganimals

• Alinkbetweensaltuseandareductioninbloathasnotbeenestablishedinreplicatedexperiments

• Accesstosaltinlatepregnancymayincreasetheriskofbearingsinewes

• SaltfertilizationofpasturewithadequateNacontent(0.12-0.20%Na)mayincreasefeedintakeandthereforeanimalproduction

SodiumandBloat 7.1

“ManyyearsagowestartedusingCustomblendfertilizersuppliedbyBobEdmeades.Includedwiththemixwassaltwhichwasappliedat50kg/hatwiceyearlywiththecapitalfertiliser.Bloathasnotbeenanissueonthefarmforyears.Wepurchasedaneighbouringfarmthatwasexperiencingbloat.OurcurrentfertilizersupplierisRavensdownandafter3yearsofsaltapplicationat50kg/hatwiceyearlybloatisnolongeranissue.Neitherfarmusesbloatoil.Thecommonfactorappearstobethesaltapplication.Idon’tknowhowitworksbutsaltischeap,probablythecostofacoupleofdrumsofbloatoil,andIappreciatethefactthatIdon’thavebloatedcows”.RexBates,DairyFarmer,Tokoroa.

“WithadryingclimatehereinsoutheastMarlboroughadaptationisthenameofthegame.Eightyearsofalmostcontinuousdroughtbetween1996and2004,hasledustomakesomefundamentalchangestoourfarmsystem.

Theheartofthechangeshasrevolvedaroundmatchingourdrymatterproductioncurvewithourdrymatterrequirementcurve.Withrainfallreducinginouralreadydryarearyegrassandclovershaveprovedtobeoflittlevalue.Ouronlyhopetomaximiseouropportunitiesistogrowplantswhichgrowproductquicklyduringouralwaystooshortspring.

Eightyearsagowestartedreplacingourgrasspastureswithlucerne.Likeanychangesomeproblemswereencountered.Oneofthesewasbloat.Ihadneverhadaproblemwithbloatinsheep,butsuddenlywehadahugeproblem.OnenightIwasdiscussingwithaneighbourthisproblem.Doyoufeedsaltheasked?Not

Areas of Uncertainty

muchIreplied.HalfanhourlaterIwasoutinthedarkplacingasaltblockforeachmobofewes.Fromthispointonourproblemhasallbutgone.Lucerneisverysodiumdeficient,soaddingsodiumisessential.

Forthelasttwoyearswehaveachievedaveragegrowthratesof390gperdayinallourewes’lambsand275inourhoggetslambs.Thismeansweweanbighealthyewelambswhichareeasytogetinlambandhave90%ourexportlambsallprocessedbymidDecember.

Ourewesandcowsnowlicktheirwaythroughthreetonneofmultimineralblocks,andthisalongwithothersupplementslikeLambSurvivalDrencharekeytoourwonderfulhealthyproductionsystem.”-DougAvery,LakeGrassmere,Marlborough

SodiumandBearings 72

Bearings (vaginal prolapse) are most common in ewes near lambing. Most farms experience a low level of incidence (<1% of ewes affected) but serious outbreaks on individual farms can affect 10% of ewes. M&WNZ R&D Brief #120 (40) estimate that financial losses in a 2,500 ewe flock with 1% bearings to be round $3,000 each year. In addition, there are animal welfare issues to consider.

An epidemiological farm study carried out by R.Hilson et al (41) reported access to salt in late pregnancy as a potential risk. It was hypothesized that higher salt intake could lead to higher water intake, and bladder/muscle interactions could promote prolapse. This theory has not been tested with controlled trials. The study involved 113 farms in 2000 and 88 farms in 2001. Farms were located in Hawkes Bay and

Southland. Hilson cautioned the transfer of these conclusions to wider sheep populations. Farmer observations suggest that offering salt blocks to salt-starved ewes a few days before lambing is not a good idea. Salt stimulates appetite so this combined with salt gorging may increase the risk of bearings through the mechanisms hypothesized by Hilson. Salt gorging is rarely observed in flocks that have continuous access to salt.

Saltfertilizationmayincreasepastureintake 7.3

Chiy et al (42, 43) reported that the application of sodium fertilizer to perennial ryegrass modified dry matter digestibility, water soluble carbohydrates, protein contents and increased rumen pH. In separate experiments they noted the productivity of ruminants is increased when pasture is fertilised with sodium because cows eat more (44). The intake of DM increases, there is an increase in the rumen turnover rate and this promotes more post-ruminal digestion. The research was carried out in the UK and published in several scientific papers. Their grazing experiments were conducted on ryegrass dominant pasture with adequate Na content (0.2%). Salt fertilization increased herbage Na to 0.5%. Milk production increased 20% from 12 kg/cow/day to 14.5.

Chiy and Phillips work has attracted a lot of attention. There are, however, few positive reports from other similar experiments. The responses reported by Chiy and Phillips may be due to short-term effects on cow grazing preference or rumen physiology rather than alleviation of deficiency (1)

References 8.0

(1) Underwood, E.J. and Suttle, N.F. 1999. The mineral nutrition of livestock (3rd edition). CAB International, UK.

(2) Kurlansky, M. 2002. Salt: a world history. pub. Jonathan Cape, pp.484

(3) Aspinall, R.J.; Mandaluniz, N.; Hight, L.J.; Lucas, R.J. 2004. Sodium deficiency in Canterbury and Central Otago sheep pastures. Proceedings of the New Zealand Grassland Association 66: 227-232.

(4) Smith, G.S., Middleton, K.R., Edmonds, A.S. 1978. A classification of pasture and fodder plants according to their ability to translocate sodium from their roots into aerial parts. New Zealand Journal of Experimental Agriculture 6: 183-188

(5) Kolver, E.S. (1999). Pasture digestion in response to change in ruminal pH. Proceeding of the New Zealand Society of Animal Production 1999, vol 39.

(6) Hemingway, R.G (1995). Requirements for sodium by livestock and dietary allowances. Sodium in Agriculture -C.J.C Phillips & P.C. Chiy 1995. 145-161.

(7) . Towers, N.R.; Smith, G.S.1983. Sodium (Na). In Grace, N.D.ed., The Mineral Requirements of Grazing Ruminants. New Zealand Society of Animal Production, pp 115-124

(8) Metson, A.J. 1962. New Zealand single factor maps. Wellington, DSIR.

(9) Edmeades, D.C., Wheeler, D.M., Clinton, O.E. 1985. The chemical composition and ionic strength of soil solutions from New Zealand topsoils. Australian Journal of Soil Research 23: 151-165

(10) Edmeades, D.C.; O’Connor, M.B. 2003. Sodium requirements for temperate pastures in New Zealand: a review. New Zealand Journal of Agricultural Research 46:37-47.

(11) Monaghan, R., Paton, J., Smith, C. 2001. Cation balances on dairy farms and implications: South Island. News you can use. Hamilton, New Zealand, Celentis Analytical

(12) Ledgard, S.F., Roach, C., Sprosen, M., Rajendram, G. 2001. Cation balances on dairy farms and implications: North Island. News you can use. Hamilton, New Zealand, Celentis Analytical

(13) Chiy, P.C. & Phillips, C.J.C (1995). Sodium in Ruminant, Production, Reproduction and Health. Sodium in Agriculture. CJC Phillips and PC Chiy

(14) O’Connor, M.B.; Hawke, M.F.; Waller, J.E.; Rotheram, J.R.; Coulter, S.P. 2000. Salt supplementation of dairy cows. Proceedings of the New Zealand Grassland Association 62: 49-53

(15) O’Connor, M.B.; Addison, B.; Miller, A.D. 1989. The effects of topdressing dairy pastures in the Waikato with sodium chloride. Proceedings of the New Zealand Grassland Association 50: 83-87

(16) Smith, G.S.; Young, P.W.; O’Connor, M.B. 1983. Some effects of topdressing pasture with sodium chloride on plant and animal nutrition. Proceedings of the New Zealand Grassland Association 44: 179-185

(17) McDonald, K.A.; Lile, J.A.; Lancaster, J.A.S.; Coulter, M.; O’Connor, M.B. 2002. Proceedings of the New Zealand Society of Animal Production 62: 236-239

(18) McLeay, L. M.; Waller, J.E.; O’Connor, M.B.; Hobson, B.L. 2002 Reticular groove contraction in dairy cattle following drenching with anti-bloat and a mixture of anti-bloat and NaCl. New Zealand veterinary journal

(19) Berger, L.L 2001. Salt and Trace Minerals for Livestock, Poultry and Other Animals

(20) Smith, E.F.; Parrish, D.B. 1950. The influence of salt on the gains of steer calves. Kansas Agr. Exp. Sta. Circular 265.

(21) Smith, E. F.; Parrish, D.B.; Splitter, E.J. 1971. The effect of withholding salt on the growth and condition of steers. Kansas Agr. Exp. Sta. Cir. 273

Use of Salt in New Zealand Pastoral Farming References

(22) Murphy, G.M.; Plasto, A.W. 1973. Live weight response following Sodium Chloride supplementation of beef cows and their calves grazing native pasture. Australian Jour. Exp Agr. And An. Husb. 13:369.

(23) Joyce, J.P.; Brunswick, L.C.F. 1975. Sodium supplementation of livestock grazing lucerne. Ruakura Farmers Conference Proc.

(24) Hawke, M.F.; O’Connor, M.B. 2002. Salt Block Supplementation to Cattle. Report prepared for Dominion Salt Ltd.

(25) Hawke, M.F.; O’Connor, M.B.; Waller, J.; Macdonald, K.A.; Hobson, B.; Coulter, S. 2002. Salt (NaCl) use in New Zealand pastoral agriculture - a summary of recent trial results. Proc. NZ Grassland Association 64: 191-196

(26) Harbers, L.H.; Harrison, K.F.; Richardson, D.; Smith, E.F. 1972. Whole corn rations for finishing heifers: A comparison of self- fed and mixed supplement, with and without salt. Kansas Agr. Exp. Sta. Bull. 557, p.46

(27) Anderson, P., Miller, A.D., Blair, I. Salt Trials - not published

(28) NRC. 1981. Nutritional Requirements for Goats. National Academy Press. Washington, DC

(29) Meyer, J.H., R.H. Grummer, P.H.Phillips and G Bohstedt. 1950. Sodium Chloride and Potassium Requirements of Growing Pigs. J. An Sci. 9:301

(30) Hagsten, I. and T.W.Perry. 1976. Evaluation of Dietary Salt Levels for Swine. I. Effect on Gain, Water Consumption and Efficiency of Feed Conversion. J.An. Sci. 42:1187

(31) Estal, C.M. Purdue University Agr. Exp. Sta. Mimeo Circulars No.18 (1945): No.20 (1946); No.23 (1947); and No.28 (1947)

(32) NRC. 1998. Nutrient Requirements of Swine 10th Ed. National Academy Press. Washington, D.C.

(33) NRC. 2001. Nutrient Requirements of Dairy Cattle: Seventh Revised Edition. National Academy Press

(34) Gillespie, B.J.; Lucas, R.J.; Moot, D.J.; Edwards, G.R. 2006. Can topdressing with salt increase oversowing success and pasture quality on steep, south facing slopes in hill country pastures? Proceedings of the New Zealand Grassland Association 68:349-353

(35) Pownall, D.B.; Lucas, R.J.; Ross, A.D. 1980. Effects of soil-contaminated feed on dry matter and water intake in sheep. Proceedings of the New Zealand Society of Animal Production, 40: 106-110.

(36) Turner, M.A. 1981. Dietary potassium sodium imbalance as a factor in the aetiology of primary tympany in dairy cows. Vetinerary Research Communication

(37) Carruthers, V.R.; Norton, D.H.; O’Connor, M.B. 1988. The incidence of bloat on pastures differing in K: Na ratio. Proceedings of the New Zealand Grassland Association 49: 169-170

(38) O’Connor, M.B.; Ledgard, S.F.; Carruthers, V.R.; Upsdell, M.P.; Feyter, C.; Edmeades, D.C. 1988. results from the spring 1986 bloat survey: South Auckland-Waikato. Proceedings of the New Zealand Grassland Association 49: 167-168

(39) Hall, J.W. and Majak, W. 1992. Rapid screening of feed supplements for the prevention of legume bloat. Can J. Animal Sci 72: 613

(40) Meat and Wool New Zealand, June 2006. R & D Brief #120 Coping with bearings.

(41) Hilson, R., Jackson, R., Perkins, N.R., West, D.M., Roe, A. 2003. An epidemiological study of vaginal prolapse in ewes. Proc Soc of Sheep and Beef Cattle Vets of NZ Vet Assoc 33: 203-217

(42) Chiy, C.P. and Phillips C.J.C. 1993. Sodium fertilizer application to pasture. 1. Direct and residual effects on pasture production and composition. Grass and Forage Science 48: 189-202

(43) Chiy, C.P. and Phillips C.J.C. 1993. Sodium fertilizer application to pasture. 3. Rumen dynamics. Grass and Forage Science 48: 249-259

(44) Chiy, C.P. and Phillips C.J.C. 1991. The effect of sodium chloride application to pasture, or its direct supplementation, on dairy cow production and grazing preference. Grass and Forage Science 46: 325-331

Notes

Use of Salt in New Zealand Pastoral Farming Notes

DominionSalt

etc etc etc\etc etc etcetc etc etc

DominionSalt

etc etc etc\etc etc etcetc etc etc

DominionSalt

etc etc etc\etc etc etcetc etc etc

AddressNotes

Use of Salt in New Zealand Pastoral Farming

away

laug

hing

0710

006